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Definitions of Territoriality There are many. One end of the spectrum---Odum: •“An actively defended home range” •“At the risk of offending semantic purists we are including under the heading of territoriality any active mechanism that spaces individuals or groups apart from one another, which means that we can talk about territoriality in plants and microorganisms as well as in animals.” •Huntingford and Turner---A Behaviorally defined notion. Territorial behavior has 4 components: 1. Site attachment 2. Exclusive use of the area 3. Agonistic behavior 4. Attack changes to retreat at the territory boundary Not a Home Range! Huntingford and Turner’s defns are specifically geared toward distinguishing territory from h.r. Home range is basically just the area in which an individual tends to restrict itself Example of coatis: Exclusive home ranges but not territories. food mates shelter 2. Length of Time defended. Ranges from hours to year-round 3. Defended by whom and how many? Single individuals versus mating pairs, etc. Phyletic Perspective on Territories Population-level consequences phyletic a. Biol. Of or pertaining to the development of a species or other taxonomic group. A fatal blow for the Ideal Free Distribution concept. A continuum of territorial behavior across closely related species from “more primitive” to more recent/more specialized: •Percina caprodes---lake dweller, nonterritorial •Hadropterus maculatus---drive other males away from females •Etheostoma (2 spp.) defend females and remain near landmarks •E. blennoides---high aggression and fixed territories. A bit ad hoc: 1. Based on Resource that the owner gets access to: also nest sites Typically refers to an area in space rather than a mobile resource (for example red deer stag and his harem of does) Winn 1954. Territoriality in Darters (fish) Varieties of Territory Thus, Natl Seln may act to increase proportion of territorial animals in a population. Costs and Benefits of Territoriality Benefits: •Food: lasts longer, lower depletion rates, less variability in supply •Mates •Offpspring rearing (female salmon) •Lowered predation (due to nest dispersion) Costs: •Acquisition •Displays and patrolling •Possibility of injury (though not very common!) •“Single-Use” Territory •TTP (Displays and Patrolling really are costly!) Yarrow’s Spiny Lizards on Mt. Graham Studying the effects of testosterone implants in male lizards. (Marler and Moore) How Large a Territory? Another simple graphical framework: Conditional Territoriality Fitness Currency Some animals are territorial at times and downright gregarious at other times. Bellbirds in New Zealand. Extra 25 kJ/day from switching to terr. behav. under low food density X Territory Size Y The optimum occurs where the slopes of the cost and the benefit curves are equal (That is where the marginal benefits of a larger territory start to decrease faster than the costs are increasing. ) Curve shapes will depend on environmental quality and population size relative to limiting factors Explanations for Territory Maintenance Two interesting observations: 1. Most territory owners don’t forfeit their territories in conflicts with intruders 2. Things don’t often escalate to full-blown fighting Rypstra (1989) studying a social spider: •Low Food Density---solitary and highly territorial •Hi FD---social. aggregations spin webs and individuals are free to go where they will. Fewer insects escape from the group webs. •The bee-eater mystery •One would expect that individuals that voluntarily choose to be non-territorial will do so because there is not an energetic advantage to holding the territory. The Resource-holding Power Asymmetry Hypothesis Territory owners are bigger and stronger by nature. Speckled wood butterfly and sunspot territories. (Davies 1978) Live in mudbank colonies, but forage in separate foraging territories that they defend against intruders Communal feeding area close to home: 100 mg insect/hour average Defended, distant territories 250 mg insect/hour average! Yet, some birds abandoned their territory to feed close to home. Why?!?! Once again (as in the starling, central place foraging example---bringing food back to chicks The Payoff Asymmetry Hypothesis There are certain costs to establishing a new territory, initially This generates predictions: but then the payoffs increase over time because you have an “agreement” with your familiar neighbors Why could this be? We’ll look at three explanations. 1. The “Arbitrary Rule” ESS hypothesis: African Bee-eaters: Beewolf wasps (O’Neill 1983) Pseudoscorpions (Zeh et al. 1997) Damselflies, endurance flying, and fat reserves (Marden and Waage 1990) But note red-winged blackbirds (Shutler and Wetherhead 1991) Two testable predictions: 1. If you remove an individual, and let somebody take over his territory, he is less likely to regain his territory if you keep him captive longer 2. The duration of contest to regain the territory should increase with increasing time of being away from its original territory Krebs 1982: found these trends BUT---not a properly controlled experiment